Hydrophilic hollow fiber ultrafiltration membranes that include a hydrophobic polymer and a method of making these membranes

Abstract

A hydrophilic membrane that includes a hydrophobic polymer and a water-soluble polymer-metal complex is provided. This membrane is made by heating a mixture of a hydrophobic polymer, a metal compound, and a water-soluble polymer. The water-soluble polymer forms complexes with the metal compound and homogeneously entangles with the dissolved hydrophobic polymer to form a viscous dope. The dope is extruded through an annular orifice to form a hollow fiber. The fiber is put in an environment having a controlled humidity so that it becomes partially solidified, and then, the fiber is put in a coagulation bath. The hollow fiber is formed by phase inversion in the coagulation bath and is collected using a take-up wheel that is partially immersed in a leaching bath.

We claim:  
     
       1. A hydrophilic hollow fiber membrane comprising: 
       a hydrophobic polymer; and  
       a water-soluble polymer transition metal complex entangled with said hydrophobic polymer, wherein said water-soluble polymer is selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrridine, and combinations thereof.  
     
     
       2. The membrane of  claim 1 , wherein said membrane has a tensile strength of about 200 to 700 psi. 
     
     
       3. The membrane of  claim 1 , wherein said membrane has a water flux of about 100 to 1500 gfd at about 40 psi. 
     
     
       4. The membrane of  claim 1 , wherein said membrane has a rejection towards a 150 k Dextran molecular weight marker ranging from about 5% to 99.9%. 
     
     
       5. The membrane of  claim 1 , wherein said hydrophobic polymer is a synthetic polymer capable of forming a film or fiber and is selected from the group consisting of polyvinylidene fluoride, polyetherketone, polypropylene, polyethylene, and combinations thereof. 
     
     
       6. The membrane of  claim 1 , wherein said membrane is comprised of polyvinylidene fluoride and a polyvinylpyrrolidone and iron complex. 
     
     
       7. The membrane of  claim 1 , wherein said membrane is an ultrafiltration membrane. 
     
     
       8. The membrane of  claim 1 , wherein said water-soluble polymeric component is permanently anchored in said hydrophobic polymer membrane matrix. 
     
     
       9. The membrane of  claim 1 , wherein said water-soluble polymeric component cannot be washed out of said membrane matrix with water or bleach comprised of 12.5% sodium hypochlorite. 
     
     
       10. A method of making a hydrophilic hollow fiber membrane, comprising: 
       mixing a hydrophobic polymer and a solvent to form a mixture;  
       heating said mixture to form a solution;  
       adding a transition metal compound and a water-soluble polymer is selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrridine, and combinations thereof to said solution;  
       heating and mixing said solution, wherein said water-soluble polymer forms complexes with said transition metal containing compound and homogeneously entangles with said dissolved hydrophobic polymer to form a viscous dope; and  
       extruding said dope through an annular orifice to form a hollow fiber.  
     
     
       11. The method of  claim 10 , further comprising: 
       feeding said fiber into a coagulation bath, wherein said fiber is formed by phase inversion in said coagulation bath.  
     
     
       12. The method of  claim 11 , further comprising: 
       feeding said fiber through an environment having a controlled humidity so that said fiber becomes partially solidified before said fiber enters said coagulation bath.  
     
     
       13. The method of  claim 11 , further comprising: 
       collecting said hollow fiber with a take-up wheel partially immersed in a leaching bath.  
     
     
       14. The method of  claim 13 , wherein said leaching bath is comprised of a nonsolvent and has a temperature of about 0.1 to 100° C. 
     
     
       15. The method of  claim 13 , wherein said hollow fiber is formed at a rate of about 5 to 300 ft/min. 
     
     
       16. The method of  claim 11 , wherein said coagulation bath is comprised of about 0% to 60% v/v of said solvent and is at a temperature of 0 to 100° C. 
     
     
       17. The method of  claim 10 , wherein said heating steps (b) and (d) take place at a temperature from 0° C. to the boiling point of the solvent, allowing said dope to be mixed under the reflux of the solvent. 
     
     
       18. The method of  claim 10 , wherein said viscous dope has a viscosity of about 100 to 600,000 centipoise (cp) at about 25° C. 
     
     
       19. The method of  claim 10 , wherein said environment has a relative humidity of 0 to 100% and a temperature range from 0 to 100° C. 
     
     
       20. The method of  claim 19 , wherein said humidity is provided by a column having a waterfall at the interior surface of said column and wherein said column maintains between about 50 to 100% relative humidity at various temperatures. 
     
     
       21. The method of  claim 10 , wherein said solvent is a polar solvent. 
     
     
       22. The method of  claim 21 , wherein said polar solvent is selected from the group consisting at dimethyl acetamide, N-methyl pyrrolidone, dimethyl formamide, dimethylsulfone, trialkylphosphate, and combinations thereof. 
     
     
       23. The method of  claim 10 , wherein said metal containing compound is comprised of an electron acceptor that is capable of forming complexes with a variety of ligands.